A year after two bombs exploded at the Boston Marathon finish line, the city and race organizers have overhauled rules and procedures surrounding the run in order to ensure the safety of participants and fans. Drawing on the hard lessons learned from the bombing, the Boston Athletic Association (BAA), the city government and law enforcement have put into place more prohibitions, guidelines, security and structure for Monday's event.

Bigger field: An additional 9,000 runners will race, for a total of 36,000 and the second-largest Boston Marathon ever. Authorities expect about a million spectators, twice as many as usual. Fortunately for the participants, this doesn't mean a more crowded starting line, but rather an additional "fourth wave" at the start and longer intervals between waves of runners. (Wave and corral assignment are based on bib number, which will also be color coded.)

As Dave McGillivray, who's been the race director for 26 years, put it, "by the time the first wheelchair crosses the finish line … the last person will not have even crossed the starting line".

Runner and spectator rules: Bags will be prohibited around the starting line in Hopkinton, along the course, and at the finish line in Boston Common. They'll also be banned on buses between Boston Common and Hopkinton. On the Common, police will check runners' gear in to be retrieved later, and they'll direct runners to pick up a clear bag, as well as their official running bib.

Participants can bring extra shoes to the start if they carry them without a bag, and food, drinks, and portable toilets will be at the Athletes' Village in Hopkinton. There will be reduced parking, as well, as the usual no parking zones will be extended farther and into more neighborhoods. The MBTA will be running normally, and there will be an unclaimed gear check running after 7pm Monday.

Runners can bring a blanket or towel to sit on (if it's not in a bag) – but they have to either check the items at Boston Common or discard them in Hopkinton.

What the BAA won't allow: backpacks or "any similar item carried over the shoulder", handbags, suitcases, rolling bags, large hydration systems (eg CamelBaks), any vest that's not a "lightweight running vest", props such as sporting or military equipment, flags bigger than 11in by 17in, and "any item larger than 5in by 15in by 5in". Cyclists and marchers are also banned from the course, and runners who like to dress up are prohibited from wearing "bulky outfit[s] extending beyond the perimeter of the body" and anything that covers their faces.

Moreover, anyone who's not registered to run and tries to jump onto the course – aka a "bandit" – is "subject to interdiction", or as McGillivray euphemistically put it, "This is just not the year to be trying to do that." The BAA has astern, understanding note about fans who want to support runners and the city, and recommends other venues (like the BAA 5K and Boston Marathon World Run) for showing your support.

The police, with more than 3,500 officers patrolling – twice as many as last year – will be watching everyone, and will have erected more barricades and checkpoints along the course than ever before. McGillivray warns that patience is necessary: "Access to almost any area will be slower than in the past. The earlier you arrive the smoother the process will be."